Android实现单线程轮循机制批量下载图片

class imageViewTask{ 
  String path; 
  Bitmap bitmap; 
  int position; 
 } 

// 任务集合 

 private List imageviews = new ArrayList(); 

// 获得图片bitmap 
  workThread = new Thread(){ 
   public void run() { 
    while(isLoop){ 
     if(!imageviews.isEmpty()){ 
      try { 
       Message msg = new Message(); 
   // 获得图片的bitmap 
       msg.obj = GetImageviewBitmap(); 
       msg.what = HANDLER_LOAD_IMAGEVIEW_SUCCESS; 
   // 发消息给主线程 
       handler.sendMessage(msg); 
        
      } catch (IOException e) { 
       e.printStackTrace(); 
      } catch (Exception e) { 
       e.printStackTrace(); 
      } 
       
     }else{ 
      synchronized (workThread) { 
       try { 
        //任务队列为空则等待 
        workThread.wait(); 
       } catch (InterruptedException e) { 
        e.printStackTrace(); 
       } 
      } 
     } 
      
    } 

//GetImageviewBitmap()方法 

// 获得图片的bitmap 
   private imageViewTask GetImageviewBitmap() throws Exception, IOException { 
    imageViewTask ivt = imageviews.remove(0); 
    String uri = BasicUri.BasicHttpUri+ivt.path;  
    HttpEntity entity = new HttpUtils().SetHttp(uri, HttpUtils.GET_METHOD, null); 
    byte[] bytes = EntityUtils.toByteArray(entity); 
    Bitmap bitmap = BitmapUtils.loadBitmap(bytes, 50, 50); 
    // 将网上下载的图片存入缓存集合中 
    map.put(ivt.path, new SoftReference(bitmap)); 
     
    ivt.bitmap = bitmap; 
    return ivt; 
   } 
  }; 
  workThread.start(); 
 } 

public class HttpUtils { 
  
 public final static int GET_METHOD = 1; 
 public final static int POST_MEHTOD = 2; 
  
 /** 
  * 构造方法 
  * @param uri 路径 
  * @param method 发送消息模式 GET_METHOD用get方式传送消息 POST_MEHTOD用post方式传送消息 
  */ 
 public static HttpEntity SetHttp(String uri, int method, List pairs) throws Exception{ 
  HttpClient client=new DefaultHttpClient(); 
  HttpResponse resp = null; 
  switch (GET_METHOD) { 
  // 用get方式发送消息 
  case GET_METHOD: 
   HttpGet get=new HttpGet(uri); 
   resp=client.execute(get); 
   break; 
  // 用post方式发送消息 
  case POST_MEHTOD: 
   HttpPost post=new HttpPost(uri); 
   HttpEntity entity=new UrlEncodedFormEntity( pairs, "utf-8"); 
   post.setEntity(entity); 
   post.setHeader("Content-Type", 
     "application/x-www-form-urlencoded"); 
   resp=client.execute(post); 
   break; 
  } 
  return resp.getEntity(); 
 } 
 } 

// 给imageview设置标记 
  holder.iv.setTag(position); 
// 增加任务队列 
  imageViewTask task = new imageViewTask(); 
  task.path = musics.get(position).getAlbumpic(); 
  task.position = position; 
  imageviews.add(task); 
  // 通知工作线程可以下载图片了 
  synchronized (workThread) { 
   workThread.notify(); 
  } 

// handler 
 private Handler handler = new Handler(){ 
  public void handleMessage(android.os.Message msg) { 
   switch (msg.what) { 
   case HANDLER_LOAD_IMAGEVIEW_SUCCESS: 
     // 更新UI 
     imageViewTask ivt = (imageViewTask) msg.obj; 
     ImageView iv = (ImageView) listview.findViewWithTag(ivt.position); 
     if(iv != null){ 
      if(ivt.bitmap != null) 
       iv.setImageBitmap(ivt.bitmap); 
     }else{ 
      iv.setImageResource(R.drawable.ic_launcher); 
     } 
     
    break; 
 
   } 
  }; 
 };